In a conventional image forming apparatus, the type of recording material (hereinafter also referred to as the type of paper) is set by a user with a setting using a computer or the like serving as an external apparatus or an operation panel provided in a main body of the image forming apparatus. In order to reduce burdens of such a user setting made from a computer or operation panel, an image forming apparatus that includes a sensor or the like serving as a determining device for determining the type of paper and that has a function of automatically determining the type of paper has been provided in recent years.
For example, PTL 1 suggests a method for applying ultrasonic waves to a recording material and detecting ultrasonic waves that are reflected from or pass through the recording material, thereby determining the surface properties and thickness of the recording material. Also, PTL 2 suggests a method for applying ultrasonic waves in an image forming apparatus in a state where no recording material is placed in order to adjust an initial value of ultrasonic waves, and controlling an output value of driving signals for driving ultrasonic waves that are transmitted to determine the type of paper of a recording material on the basis of a received voltage value of ultrasonic waves received by an ultrasonic sensor on a receiver side.
However, since driving signals are controlled with no recording material being placed, the driving signals controlled with no recording material being placed are not necessarily optimized for detecting a basis weight in a case where basis weights of various recording materials, such as thin paper having a small basis weight to thick paper having a large basis weight, are to be detected. For example, assume that a driving signal that is adjusted with no recording material being placed is suitable for detecting a basis weight of ordinary paper, then a small output value is obtained in a recording material that is so-called thick paper having a basis weight of 120 g/m2 or more, which causes the possibility of determination of the type of paper being difficult. Also, a large output value is obtained in a recording material that is so-called thin paper having a basis weight of 75 g/m2 or less and the output value is saturated, which causes the possibility of determination of the type of paper being difficult.
The invention according to the present invention has been made in view of the above-described circumstances, and an object thereof is to appropriately control driving signals in accordance with a recording material and to output ultrasonic waves in accordance with the recording material.